U.S. President Donald Trump arrives at an event to celebrate the anniversary of first lady Melania Trump's “Be Best” initiative in the Rose Garden at the White House in Washington, U.S., May 7, 2019. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - President Donald Trump on Wednesday asserted executive privilege over Special Counsel Robert Mueller’s report and its underlying investigative materials, escalating a battle with the Democrats on the U.S. House Judiciary Committee.

The move, announced by the Justice Department in a letter to House Judiciary Committee Chairman Jerrold Nadler, came just minutes before the panel was poised to vote to hold Attorney General William Barr in contempt for defying a congressional subpoena to hand over the full unredacted report.